The present invention relates to magnetic recording heads for reading and writing on a magnetic recording surface and, more particularly, to improved mounting arrangements for such magnetic heads.
Magnetic recording heads of the type commonly used for reading and writing on magnetic recording means such as rotating magnetic recording disks and rotating magnetic recording drums, are often used for recording digital information at extremely high densities. As the density at which digital information is recorded on a magnetic recording surface is increased, the gap between the recording head and the magnetic recording surface must be decreased. The smaller the gap and the closer the magnetic head is positioned with respect to the recording surface, the more difficult it becomes to control the mechanical tolerances of the structure mounting the recording head. To overcome these mechanical difficulties, mechanical recording heads are placed in head assemblies adapted for floating on a thin film of air created by the laminar air flow due to the rotation of the recording surface.
In such systems, when the recording medium rotates, the laminar air flow causes the head assembly to be forced away from the medium. Therefore, some urging means, such as a spring, must be provided to overcome this air flow and counterbalance the head assembly, keeping it as close to the recording medium as possible.
Floating magnetic recording head assemblies are often mounted in gimbal mounting devices in order to allow the angle and position of the magnetic recording head assembly to conform to the air bearing.
Frequently, gimbals are arranged for free frictionless gimbaled action. However, a completely free moving and frictionless gimbal is undesirable for floating magnetic recording head assemblies. For example, during disk runout or with the occurrence of air turbulence as the head assembly is being moved into a floating position with respect to the magnetic recording surface, the distance between the assembly and the recording surface will vary and the head assembly may be caused to rotate and strike the recording surface thereby causing damage to the recording surface and/or the head assembly. Furthermore, the angle of a head assembly mounted in a free frictionless gimbal is unstable. As a result, as the head is moved into a recording position, it may quite possibly rotate at an angle allowing the edge or corner of the head assembly to strike the recording surface.
In order to overcome the aforementioned disadvantages, springs capable of applying increased amounts of force to the head have been used in an attempt to provide restrained movement of the assembly and to overcome undesired head yaw of the assembly as, for example, the laminar air flow increases and decreases and to enable the show of the assembly to properly float upon the nearly impenetrable barrier created upon the recording surface by the air flow. However, this arrangement is generally quite complex requiring accurately machined parts and, moreover, the increased spring force applied to the assembly causes wear on both the recording surface and the assembly and may score the surface at slow speeds while stopping and starting because the force applied by the springs is constant and usually greater than that required to break through the laminar air flow.
Other conventional type gimbal mountings for recording head assemblies are, for example, disclosed in U.S. Pat. No. 3,320,599, issued May 16, 1967 to Billawalla and U.S. Pat. No. 3,864,749, issued Feb. 4, 1975 to Stansell. The gimbal springs disclosed in these patents comprise an intricate network of either four or six elongated perforations incorporated in a rectangular body structure including a head support surface adapted to be connected to and carry the recording head assembly. The body structure further includes oppositely positioned ears for connecting the spring to a head actuator assembly. Typically, the head support surface is elongated and adapted to be secured to the non-bearing surface or back of the head, across the entire length thereof.
The disadvantage inherent in such a structure is the generally high degree of stiffness of the head support surface as compared to that of the perforated or leaf portion of the structure which gives rise to substantial movement of the head assembly in the roll direction, e.g., during positioning actuation of the head and in the presence of air turbulence intermediate the bearing surface of the head and the recording surface. Also, it has been found that such a support surface provides less rigidly in the yaw direction.
Further enhancing roll of the head assembly is the arrangement of mounting the spring support to the non-bearing surface in a plane parallel to but above the line through the center of mass. Also, in the spring arrangement under discussion, the usual actuator plunger or piston moves the head into its actuated position by way of spring, i.e., there is no direct point of actuating engagement between the piston and the load point of the head which, generally speaking, provides for poor flying stability due to the forces acting upon this point remote from the line through the center of mass of the head.
Still further, this type of gimbal spring for mounting magnetic recording heads has excessive play in the structure thereof and allows the head assembly mounted thereto to substantially rotate around an axis perpendicular to the recording surface or to move parallel relative to the recording surface. This is of great disadvantage as far as high recording densities are concerned.